Electrical distribution system



Nov. 25, 1941.

W. H. FRANK ELECTRICAL DISTRIBUTION SYSTEM Filed Feb. 23, 1940 5Sheets-Sheet l m /2' g If #1, WI

INVENTOR.

ATTORNEY.

Nov. 25, 1941. w. H. FRANK 2,264,075

ELECTRICAL DISTRIBUTION SYSTEM Filed Feb. 23, 1940 5 Sheets-Sheet 2INVENTOR. BY w w ATTORNEY.

Nov. 25, 1941. w. H. FRANK 2,264,075

ELECTRICAL DISTRIBUTION SYSTEM Filed Feb. 23, 1940 5 Sheets-Sheet 3ATTORNEY.

Nov. 25, 1941; w. H. FRANK 2,264,075

ELECTRICAL DISTRIBUTION SYSTEM Filed Feb. 23, 1940 5 Sheets-Sheet 4 I IINVENT OR. BY f ATTORNEY.

I ATTORNEY.

Nov. 25, 1941; w. H. FRANK ELECTRICAL DISTRIBUTION SYSTEM Filed Feb. 25,1940 5 Sheets-Sheet 5 Patented Nov. 25, 1941 ELECTRICAL DISTRIBUTIONSYSTEM William H. Frank, Detroit, Mich, assignor to Bulldog ElectricProducts Company, Detroit, Micli., a corporation of West VirginiaApplication February 23, 1940, Serial No. 320,454

(Cl. I'm-334.1)

27 Claims.

This application relates to electrical distribution systems of the busduct type as shown in a prior application, Serial No. 231,712, ofSeptember 26, 1938, now abandoned.

Bus duct systems have been known before. For example, Patent No.2,041,675 of May 19, 1936, discloses a bus duct system. This applicationrelates specifically to an improved bus duct system.

The system of this application is simple in form, inexpensive tomanufacture, easy to take apart for replacement or repair of any partthat might prove to be defective and contains many novel features.

The system hereof is so constructed that it effectively solves a seriousproblem found in the use of bus duct systems, namely the problem ofdestruction due to power arcs which start in the space between the busbars and the metal duct commonly used.

A bus duct system employs branch circuit takeoff devices, commonly knownas plugs, having prongs for engaging the bus bars despite that theprongs directly engage and make contact with the bus bars. I am able toinsulate the bus bars on their outside surfaces, even at prong engagedpoints. This is because the system is such that contact between the plugprongs and the bus bars is made, not on the outside of the bus bars, asis conventional, but on the insides of the bus bars, these being madehollow for this purpose. In this way, the bus bars may be insulated ontheir outside throughout their entire length. Consequently, power arcswill not arise,

. because these arcs arise only at uninsulated points of the bus bars.

In the system hereof novel splices are provided for the bus bar ends,and these splices are so designed that they permit the bus bars to beinsulated on their outsides continuously, even at the splices. e

A feature of the system hereof is the novel arrangement for providinginsulated openings through which plug prongs are inserted. At

such openings there is provided a hollow insulator through which the busbar passes and having an opening or well through which the plug prongpasses,-the opening being sealed from the inside of the duct exceptwhere it intercepts the opening through which the bus bar passes.

In this way, a prong inserted into the duct through the prong opening ofthe insulator is sealed from the inside of the duct. The insulator islongitudinally movable so that part thereof may be used as a shutter forthe duct opening, if desired.

Another feature is a novel construction of the plug prong, constructedto provide a lateral resilient contact pressure on the bus bar.

Another feature is a novel arrangement for drawings.

mounting insulators in th duct using shock absorbing material betweenthe ductwall and the insulator.

The system hereof is shown in the appended In these drawings:

Fig. 1 is a fragmentary plan view of part of a bus duct run showing abranch plug in place;

Fig. 2 is an elevation view with the branch plug shown in the ONposition; the branch plug hole is shown as open; and the insulatorclosure therefor is shown in the open position;

Fig. 3 is a view like Fig. 2 but showing the branch plug in th OFFposition; the plug prong hole is shown as closed by the movableinsulator;

Fig. 4 is a transverse view;

Fig. 5 shows a plug prong detail;

Fig. 6 is a plan view with no plug shown; this figure shows theinsulator utilized as a closure for the plug prong hole of the duct;

Fig. 7 is an elevation view of Fig. 6;

Fig. 8 is a cross section of one form of bus bar;

Fig. 9 shows how bus bars are spliced;

Fig. 10 is a section on line l0--|0 of Fig. 9;

Fig. 11 shows a compound bus bar;

Figs. 12 and 13 are sections on corresponding lines of Fig. 11;

Fig. 14 is an isometric view of the insulator shown in earlier figuresof the drawings;

Fig. 15 is a section on line I5-i5 of Fig. 14;

Fig. 16 shows a duct equipped with a modified form of insulator;-

Fig. 17 is an isometric view of the insulator per se;

Figs. 18 and 19 are views on corresponding lines of Fig. 17;

Fig. 20 is a cross section showing a modified arrangement for supportingthe insulators in the duct;

. 21 shows a novel plug prong;

. 22 is a section on line 22-22 of Fig. 21; 23 is a side view of theprong;

. 24 shows a novel bus bar;

. 25 is an end view;

-. 26 is a section on line 2626 of Fig. 24;

Fig. 27 is a novel splicing arrangement for bus bars;

Fig. 28 is a section on line 28-28 of Fig. 27. I It will be understoodthat the electrical distribution system herein disclosed is generally ofthe type disclosed in Patent No. 2,041,675 of May 19, 1936, to WilliamH. Frank and Joseph W. Harper. As a matter of fact the sheet metalcasing halves hereof, references [0, are similar except for theformation of the plug prong holes, to the casing halves 20 of thatpatent, and the arrangement used in the structure hereof for securingthe halves to each other longitudinally, and also for splicing sectionsof casing at the ends of the sections are similar to the arrangements ofthe patented system provided for the same purpose. That is to say, inthe system ,hereof the casing halves. III are of equal length and havecooperating longitudinal edge flanges ll through slotted holes of whichpass casing joining bolts l2. Splices between sections are not shown butit will be understood that the splices are effected by means of lapscarf joints,

like those described in the patent.

Within the duct formed by the casing halves are bus bars I4 and theseare insulatedly supported in the duct by means of the insulators I5,some of which are below the bus bars and some of which are above, asshown in Fig. 7. The insulators are positioned adjacent the plug prongholes [6 which are longitudinally spaced and staggered and are disposedon opposite sides of the casing. Each insulator has a grooved surfacewhose grooves l'I receive the bus bars, these being so proportioned withrespect to the grooves that when they are seated in the grooves,practically all of a bus bar at an insulator except one edge is closelysurrounded by the wall of the grooves (Fig. 4).

Each insulator is provided with a key I8 projecting through theplugprong hole I6 of the duct to enable the insulator to be slidlongitudinally for closing or opening the plug prong hole, the keyengaging edges of the hole for limiting movement of the insulator.

Each insulator is provided with a plurality of bores 19 aligned with thebus bars l4 and through which access may be had for engagement of thebus bars, engagement being effected by means of plug prongs 20 supportedon hinged covers 2| of a plug, the latter including a sheet metal box 22secured to the duct and having hinges 23 to which the cover 2| issecured. Branch circuit conductors 24, entering the box 22 through aside opening thereof, as shown in Fig. 1, are connected through fuses 25to the prongs 20.

The bus bars are shown as of channelled cross section and the prongs forengagement therewith are intended to fit within the channels of the busbars and for this purpose are formed with flared tips 26 as shown inFig. 5.

Splices between bus bars may be effected by means of the splicingsleeves 21 of Figs. 9 and 10, these receiving set screws 28 whereby afirm splice may be effected.

Instead of the bus bars being formed of a single ribbon of conductingmaterial bent in the form of the U of Fig. 8, the bus bars may be madeof two ribbons 30 of conducting material, Figs. 11 and 12, which arebuttoned to each other at intervals, as by means of the rivets 3|, Fig.13, or. welds at the spots 32 through which the rivets are shown aspassing. This type of bus bar can receive prongs 20 on either edge,inserted through either side of the duct.

Each insulator 15 functions not only as a support for the bus bars butalso as a closure for a plug prong hole l6 and as an arc chute or shieldaround the plug prongs 20. When the insulators are in the position ofFigs. 3 and 6, they close the holes of the duct, because at that time itis not intended to utilize the holes for receiving plug prongs, thereeither being no plug in place the bores in the insulator and the wallsof these bores will function as arc chutes or shields around the pointsof separation of the prongs and the bus bars.

If desired, and as is preferable, for insulation purposes, the outersurface of the bus bars may be coated with insulation, such asinsulating enamel. Further, if desired, the insides of the bus bars mayalso be coated with enamel, with the coatingto be removed at the pointswhere the bus bars are to be engaged by plug prongs.

Further, if desired, the bus duct may be filled with loose fibrousinsulating material, such as shredded asbestos, such as has beensuggested in a prior application, Serial No. 116,985 of December 21,1936, of William H. Frank, now Patent No. 2,186,377, issued January 9,1940.

Inasmuch as the insulators are staggered as well as disposed on oppositesides of the bus bars, the insulators hereof will function like those ofa prior application, Serial No. 183,144, filed January 31, 1938, byArthur S. Bassette et al., now Patent No. 2,230,423, issued February 4,1941, to prevent interruption of the coursing of arcs along the freeedges of the bus bars, for at all times, namely at each insulator andbetween insulators, each bus bar has an exposed free edge and because ofthe disposition of the insulators, the arcs travel along the bus barsmoving from edge to edge of the bus bars as they pass the insulators,all as described in such application.

Each insulator may seat in seats 33 in its sides, pads 34 of resilientmaterial, such as felt, for frictionally engaging the sides of the duct,for cushioning the insulators and for holding them firmly againstundesired moving and rattling.

In the construction of Figs. 16-19 the insulators employed, referenced40, are provided with longitudinal bores 4|, opening to the oppositesurfaces of the insulator through the opening 42 and 43; the openings 43are useful as plug prong receiving openings. Adjacent the openings" is akey 44 for cooperating with the edges of the duct hole in which the keyis disposed and which is closed normally by the insulator.

Each insulator may be provided with grooves or barriers (not shown) forproviding adequate clearance between bus bars or different polarities.

It will be observed that whereas the insulators of Figs. 17 through19completely enclose the bus bars, those of Figs. 14 and 15 do not enclosethe on the duct at that point, or if there is a plug there, the cover ofthe plug is open.

When, however, a plug is in place on a piece of duct, near a hole Hi,the insulator at such hole may be moved to the position of Fig. 2 toexpose the hole and make it possible for a plug prong to be projectedinto the duct and engage the bus bars. The plug prongs will pass throughbus bars completely.

Fig. 20 shows how the insulators l5 may be cushioned against the side ortop walls of the duct by the use of cushioning pads 50 which instead ofterminating short of the top of the duct as do the pads 33, continueover the tops of the insulators l5 to engage the top wall of the duct.

Since the bus bars are loosely mounted within the insulators, and sincethe insulators are cushioned against contact with the duct, the bus barsthemselves are cushioned with respect to the duct.

Figs. 21 to 23 show a plug prong 5| having two slots 52 dividing theprong into three strips deflected from one another and thus difieringfrom the singly slit prong 20 of Fig. 3. The prongs of Figs. 21-23provide a balanced construction insuring a lateral resilient contactpressure.

The bus bars might well be'of the form shown in Figs. 24-26. Here thebus bars, referenced 54,

have inwardly bent portions 55 for engaging plug prongs and these may beinserted into the bus the continuous opening at the top of the bus baror through the longitudinally spaced openings 56 in the bight of the busbar.

Figs. 2'7 to 28 show a splice for the bus bars differing slightly fromthat of Figs. 9 throughll. The bus bars, referenced 51, are shown ascontaining a splicing strap 58 adapted to be wedged into the bus bars 51by set screws or the like 59 of insulation material, or of insulationcapped metal, threaded through a sleeve 60 whose interior surface, aswell as its exterior surface, may be coated with insulation coatings 6|,preferably of the same character as the insulation coating 62 on theoutside of the bus bars 51. The splice herein disclosed has the virtueof providing a continuous insulation coating around the bus runs even atthe point of splicing.

It will be observed that while but one form of plug is herein disclosed,that many different forms of plugs might well be provided and the oneherein shown is disclosed only by way of example.

Now having described the system disclosed in the appended drawings,reference will be had to the claims which follow.

I claim:

1. A bus duct system comprising a sheet metal duct and containing busbars spaced from said duct andhaving unitary insulator blocks in theduct insulatedly supporting the bus bars and spacing them from the ductand through which pass the bus bars, the blocks having transverse prongreceiving openings aligned with duct openings and communicating with thebus bars and with the space outside the duct through the duct openings,the blocks being slidable longitudinally so that parts thereof may formclosures for the duct openings or so that the block openings may alignwith the duct openings to expose the bus bars.

2. A bus duct system having unitary insulator blocks in the ductinsulatedly supporting the bus bars and spacing them from the duct andthru which pass the bus bars, the blocks having transverse prongreceiving openings aligned with duct openings and communicating with thebus bars and with the space outside the duct thru the duct openings, theblocks being slidable longitudinally so that parts thereof may formclosures for the duct openings or so that the block openings may alignwith the duct openings to expose the bus bars, the blocks having keyswithin the duct openings to form handles for the blocks and also forServing as stops for the blocks.

3. A bus duct system comprising an elongated sheet metal duct or conduithaving a prong receiving opening and containing a longitudinallyextending bus bar laterally and transversely spaced from said duct, anda block having a channel through which passes the bus bar, the blockhaving near one end a transver e prong receiving opening extending fromthe outer surface of the block to the channel containing the bus bar,and also having a shutter forming portion at the other end, the blockbeing longitudinally slidable so that either its prong opening willalign with the duct opening to expose the bus bar to such opening forprong engagement, or its prong opening will be out of line and itsshutter forming portion will be in line with the duct opening wherebythe latter will be closed by the block, the block having portionssurrounding its prong opening and forming bus bar barriers.

4. A bus duct system comprising an elongated sheet metal duct or conduithaving a prong receiving opening and containing a longitudinallyextending bus bar laterally and transversely spaced from said duct, anda block having a channel through which passes the bus bar, the blockhaving near one end a transverse prong receiving opening extending fromthe outer surface of the block to the channel containing the bus bar,and also having a shutter forming portion at the other end, the blockbeing longitudinally slidable so that either its prongopening will alignwith the duct opening to expose the bus barto such opening for prongengagement, or its prong opening will be out of line and its shutterforming portion will be in line with the duct opening whereby the latterwill be closed by the block, the block having portions surrounding itsprong opening and forming bus bar barriers, the

, duct and bus bar being horizontally disposed, and

the block being below the bus bar to support the bus bar.

5. A bus duct system comprising an elongated sheet metal duct or conduithaving a prong re ceiving opening and containing a longitudinallyextending bus bar laterally and transversely spaced from said duct, anda block having a channel through which passes the bus bar, the blockhaving near one end a transverse prong receiving opening extending fromthe outer surface of the block to the channel containing the bus bar,and also having a shutter forming portion at the other end, the blockbeing longitudinally slidable so that either its prong opening willalign with the duct opening to expose the bus bar to such opening forprong engagement, or its prong opening will be out of line and itsshutter forming portion will be in line with the duct opening wherebythe latter Will be closed by the block, the block having portionssurrounding its prong opening and forming bus bar barriers, the duct andbus bar being horizontally disposed, and the block being above the busbar to be supported thereby.

6. A bus duct system comprising an elongated sheet metal duct or conduithaving a prong receiving opening and containing a longitudinallyextending bus bar laterally and transversely spaced from said duct, anda block having a channel through which passes the bus bar, the blockhaving near one end a transverse prong receiving opening extending fromthe outer surface of the block to the channel containing'the bus bar,and also having a shutter forming portion at the other end, the blockbeing longitudinally slidable so that either its prong opening willalign with the duct opening to expose the bus bar to such opening forprong engagement, or its prong opening will be out of line and itsshutter forming portion will be in line with the duct opening wherebythe latter will be closed by the block, the block having portions'surroundingits prong opening and forming bus bar barriers, andsurrounding the bus bar so that the block will be guided by the bus bar,as a rail, on block sliding movement.

7. A bus duct system comprising an elongated sheet metal duct or conduithaving a prong receiving opening and containing a longitudinallyextending bus bar laterally and transversely spaced from said duct, anda block having a channel through which passes the bus bar, the blockhaving near one end a transverse prong receiving opening extending fromthe outer surface of the block to the channel containing the bus bar,and also having a shutter forming portion at the other end, the blockbeing longitudinally slidable so that either its prong opening willalign with the duct opening to expose the bus bar to such opening forprong engagement, or its prong opening will be out of line and itsshutter forming portion will be in line with .the duct opening wherebythe latter will be closed by the block, the blockhaving portionssurrounding its prong opening and forming bus bar barriers, the blockhaving a second' opening, thelatter being atthe end of the blockopposite; the first named opening, and extending from that outer surfaceof the block opposite the outer surface to which extends the first namedopening, with the second opening also extending to the channel.

8. A bus duct system comprising an elongated sheet metal duct or conduithaving longitudinally spaced prong receiving openings and containing alongitudinally extending bus bar laterally and transversely spaced fromsaid duct, and a plurality offiongitudinally spaced blocks havingxalined channels through which passes the bus bar; each block having nearone end a transverse prong receiving opening extending from the outersurface of the block to the channel containing the bus bar, and, alsohaving a shutter forming portion at the other end, the blocks beinglongitudinally slidable so that either their prong, openings will alignwith the duct openings to expose the bus bar to such openings for prongengagement, or their prong openings will be out of line and theirshutter forming portions will be in line-with the duct openings wherebythe latter will be closed by the blocks, the blocks having portionssurrounding their prong openings and forming bus bar barriers.

9. A bus duct system comprising an elongated sheet metal duct or conduithaving longitudinally spaced prong receiving openings and containing alongitudinally extending bus bar laterally and transversely spaced fromsaid duct, and a plurality of longitudinally spaced blocks having alinedchannels through which passes the bus bar, each block having near oneend a transverse prong receiving opening extending from the outersurface of the block to the channel containing the bus barfand alsohaving a shutter forming portion at the other end, the blocks beinglongitudinally slidable so that either their prong openings will alignwith the duct openings to expose the bus bar to such openings for prongengagement, or their prong openings will be out of line and theirshutter forming portions will be in line with the duct openings wherebythe latter will be closed by the blocks, the blocks having portionssurrounding their prong openings and forming bus bar barriers, someblocks being on one side of the bus bar and some being on the other sideof the bus bar.

10. A bus duct system comprising an elongated sheet metal duct orconduit having longitudinally spaced prong receiving openings andcontaining a longitudinally extending bus bar laterally and transverselyspaced from said duct, and a plurality of longitudinally spaced blockshaving alined channels through which passes the bus bar, each blockhaving near one end a transverse prong receiving opening extending fromthe outer surface of the block to the channel containing the bus bar,and also having a shutter forming portion at the other end, the blocksbeing longitudinally slidable so that either their prong openings willalign with the duct openings to expose the bus bar to such openings forprong engagement, or their prong openings will be out of line and theirshutter forming portions will be in line with the duct openings wherebythe lat-,

in will be closed by the blocks, the blocks having portions surroundingtheir prong openings and forming bus bar barriers, some blocks being onone side of the bus bar and some being on the other side of the bus bar,with the prong openings of the blocks and duct being on opposite sidesof the bus bar to permit prong insertion from opposite sides of theduct.

11. A bus duct system comprising an elongated sheetmetal duct or conduithaving a prong receiving opening and containing a longitudinallyextending bus bar laterally and transversely spaced from the duct, and aprong way. shield or block at least partially surrounding the bus barand having a channel through which passes the bus bar and having aholeor prong way providing prong access to the bus bar, the hole orprong way connecting the bus bar channel and the outer surface of theshield, the shield also having a shutter forming or blocking portion forblocking the duct opening when the prong hole of the shield is out ofline with the duct opening, the shield being movable to aline either itsprong hole or its blocking portion with the duct opening.

12. A bus duct system comprising an elongated sheet metal duct orconduit having a prong receiving opening and containing a longitudinallyextending bus bar laterally and transversely spaced from the duct, and aprong way shield or block at least partially surrounding the bus bar andhaving a channel through which passes the bus bar and having a hole orprong way providing prong access to the bus bar, the hole or prong wayconnecting the bus bar channel and the outer surface of the shield, theshield also having a shutter forming or blocking portion for blockingthe duct opening when the prong hole of the shield is out of line withthe duct opening, the shield being movable to aline either its pronghole or its blocking portion with the duct opening, the duct and bus barbeing horizontally disposed, and the block being belowthe bus bar tosupport the bus bar.

13. A bus duct system comprising an elongated sheet metal duct orconduit having a prong receiving opening and containing a longitudinallyextending bus bar laterally and transversely spaced from the duct, anda. prong way shield or block at least partially surrounding the'bus barand having a channel through which passes the bus bar and having a holeor prong way providing prong access to the bus bar, the hole or prongway connecting the bus bar channel and the outer surface of the shield,the shield also having a shutter forming or blocking portion forblocking the duct opening when the prong hole of the shield is out ofline with the duct opening, the shield being movable to aline either itsprong hole or its blocking portion with the duct opening, the duct andbus bar being horizontally disposed, and the block being above the busbar to be supported thereby.

14. A bus duct system comprising an elongated sheet metal duct orconduit having a prong receiving opening and containing a longitudinallyextending bus bar laterally and transversely spaced from the duct, and aprong way shield or block at least partially surrounding the bus'bar andhaving a channel through which passes the bus bar and having a hole orprong way providing prong access to the bus bar. the hole or prong wayconnecting the bus bar channel and the outer surface of the shield, theshield also having a shutter forming or blocking portion for blockingthe duct opening when the prong hole of the shield is out of line withthe duct opening, the shield being movable to aline either its pronghole or its blocking portion with the duct opening, and surrounding thebus bar so that the block will be guided by the bus bar, as a rail, onblock sliding movement.

15. A bus duct system comprising an elongated sheet metal duct orconduit having a prong receiving opening and containing a longitudinallyextending bus bar laterally and transverse- 1y spaced from the duct, anda prong way shield or block at least partially surrounding the bus barand having a channel through which passes the bus bar and having a holeor prong way providing prong access to the bus bar, the hole or prongway connecting the bus bar channel and the outer surface of the shield,the shield also having a shutter forming or blocking portion forblocking the duct opening when the prong hole of the shield is out ofline with the duct opening, the shield being movable to aline either itsprong hole or its blocking portion with the duct opening, the blockhaving a second opening, the latter being 'at the end of the blockopposite the first named opening, and extending from that outersurface'of the block opposite the outer surface to which extends thefirst named opening, with the second opening also extending to thechannel.

16. A bus duct system comprising an elongated sheet metal duct orconduit having longitudinally spaced prong receiving openings andcontaining a longitudinally extending bus bar laterally and transverselyspaced from the duct, and a plurality of longitudinally spaced prong wayshields or blocks at least partially surrounding the bus bar and havingalined channels through which passes the bus bar and having a holeproviding prong access to the bus bar, the holes or prong waysconnecting the bus bar channel and the outer surfaces of the shields,the shields also having shutter forming or blocking portions forblocking the duct openings when the prong holes of the shields are outof line with the duct openings, the shields being movable to alineeither their prong holes or their blocking portions with theduct'openings.

17. A bus duct system comprising an elongated sheet metal duct orconduit having longitudinally spaced prong receiving openings andcontaining a longitudinally extending bus bar laterally and transverselyspaced from the duct, and a plurality of longitudinally spaced prong wayshields or blocks at least partially surrounding the bus bar and havingalined channels through which passes the bus bar and having a holeproviding prong access to the bus bar, the

being on one side of the bus bar and some being on the other side of thebus bar.

18. A bus duct system comprising an elongated sheet metal duct orconduit having longitudinally spaced prong receiving openings andcontaining a longitudinally extending. bus bar laterally and,

transversely spaced from the duct, and a plurality of longitudinallyspaced prong way shields or blocks at least partially surrounding thebus bar and having alined channels through which passes the bus bar andhaving a hole providing prong access to the bus bar, the holes or prongways connecting the bus bar channel and the outer surfaces of theshields, the shields also having shutter forming or blocking portionsfor blocking the duct openings when the prong holes of the shields areout of line with the duct openings, the shields being movable to alineeither their prong holes or their blocking portions with the ductopenings, with the prong openings of the blocks and duct being onopposite sides of the bus bar to permit prong insertion from oppositesides of the duct.

19. A bus duct system comprising an elongated sheet metal duct orconduit having longitudinally spaced prong receiving openings andcontaining a longitudinally extending bus bar laterally and transverselyspaced from said duct, and a plurality of longitudinally spaced blockshaving alined channels through which passes the bus bar, each blockhaving near one end a transverse prong receiving opening extending fromthe outer surface of the block to the channel containing the bus bar,and also having a shutter forming portion at the other end, the blocksbeing longitudinally slidable so that either their prong openings willalign with the duct openings to expose the bus bar to such openings forprong engagement, or

their prong openings will be out of line and their shutter formingportions will be in line with the duct openings whereby the latter willbe closed by the blo'cks,the blocks having portions surrounding theirprong-openings and forming bus bar barriers, some blocks being on oneside of the bus bar and some being on the other side of the bus bar, theduct and bus bar being horizontally disposed so that some blocks supportthe bus bar and some blocks are supported by the bus bar.

20. A bus duct system comprising an elongated sheet metal duct orconduit having longitudinally spaced prong receiving openings andcontaining a longitudinally extending bus bar laterally and 'the otherend, the blocks being longitudinally slidable so that either their prongopenings will align with the duct openings to expose the bus bar to suchopenings for prong engagement, or their prong openings will be out ofline and their shutter forming portions will be in line with the a ductopenings whereby the latter will be closed by the blocks, the blockshaving portions surrounding their prong openings and forming bus barbarriers, some blocks being on one side of the bus bar and some being onthe other side of the bus bar, the duct and bus bar being horizontallydisposed so that some blocks support the bus bar and some blocks aresupported by the bus bar, with the prong openings of the blocks and ductbeing on opposite sides of the bus bar to gerrgntprong insertion fromoppositesides of the 21. A bus duct system comprising an elongated sheetmetal duct or conduit having prong receiving openings in opposite sidesand containing a l illel y extending bus bar laterally, and ltransversely spaced from the, duct, accessible blocks to be moved withinthe duct without dissaid walls, and whose narrow edges are laterallyspaced from said walls, with each support-dis-. posed between andengaging a wall and the adjacent edge of the bus run, and each beingfree of the other wall, the supports being staggered in theirlongitudinal arrangement whereby there is but one support at any onepoint of the bus run,

, so that the narrow edges of the bus run are free assembling the duct,bus, or blocks relatively, to

and from those positions of the blocks wherein they expose or close theopenings, the blocks having transverse slots providing paths to the busbar from the duct openings when such slots are alined with suchopenings.

22. A bus duct system comprising an elongated sheet metal duct orconduit having 8. prong receiving opening and containing alongitudinally extending bus bar laterally and transversely spaced fromthe duct, accessible through said opening, an insulator block within theduct for supporting the bus bar and arranged to form a closure for saidopening when in alignment therewith, and to expose said opening when outof alignment therewith, the bus bar, block, and duct being formedrelatively to permit the block to be moved within the duct withoutdisassembling the duct, bus, or block relatively, to and from thosepositions of the block wherein it exposes the openingor closes it, theblock having a transverse slot which provides a path to the bus bar fromthe duct opening when the block is inthe position where it closes saidopening except for the slot of the block.

23. A bus duct system comprising a duct having spaced prong openings onopposite sides thereof and containing a hollow bus bar spaced from saidduct and having prong openings on opposite sides thereof alined with theprong openings of the duct, unitary insulator blocks in the ductinsulatedly supporting the bus bar and spacing it from the duct andthrough which passes the bus bar, the blocks having transverseprongreceiving openings on opposite sides of the bus bar adapted forcommunicating the interior of the bus bar with the space outside theduct through the duct openings, the blocks being longitudinally slidableto place their transverse openings into or out of alignment with the busand duct openings.

24. A bus duct including, a bus run, supports therefor, and a duct-orcasing having runs of opposed parallel walls, the bus run being a run ofwide thin ribbon whose wide faces are normal to said walls, and whosenarrow edges are laterally spaced from said walls, with each supportdisposed between and engaging a wall and the adjacent edge of the busrun, and each being free of the other wall, the supports being staggeredin their longitudinal arrangement whereby there is but one support atany one point of the bus run, so that the narrow edges of the bus runare free between alternate, similarly facing, supports, the supports andbus run having cooperating formations for laterally bracing the bus runagainst lateral shifting in a direction normal to the wide faces 01 thebus run, and adjustable means for adjustably determining the relativespacing of said walls and for holding the walls, supports, and bus runin a unitary assembly, with the relative lateral spacing of said walls,in a direction parallel to the widefaces of the bus run, beingdetermined by the'adjustment of said means.

25. A bus duct including, a bus run, supports therefor, and a duct orcasing having runs of opposed parallel walls, the bus run being, a runof wide thin ribbon whose wide faces are normal to between alternate,similarly facing, supports, the supports and bus run having cooperatingformations for laterally bracing the bus run against lateral shifting ina direction normal to the wide faces of the bus run, and adjustablemeans for adjustably determining the relative spacing of said walls andfor holding the walls, supports, and bus run in a unitary assembly, withthe relative lateral spacing of said walls, in a direction parallel tothe wide faces of the bus run, being determined by the adjustment ofsaid means, the walls having openings at the supports, the supportsbeing formed with wells registering with such openings and permittingprongs which enh ter the supports through such openings to pass throughthe supports so as to wipe the wide faces of the bus run.

26. A bus duct comprising cooperating elongated sheet metal pans whichtogether form a duct, each pan having longitudinally spaced openings,longitudinally spaced insulator blocks in each pan at such openings andformed with longitudinally extending grooves on the sides thereof mostremote from said openings and also formed with transversely extendingslots opening to said grooves and arranged to open to and aline withsaid openings, bus bars in the grooves of both sets of blocks in bothpans, and externally accessible means for fastening the pans to; eachother and thus holding the blocks and bus bars in assembly, the blocksin one pan terminating short of the opposite wall of the other pan,whereby the duct is not transversely barriered completely, but is formedto permit air to flow continuously therethrough, each busbeing hollow sothat air can flow through the bus bars,

and having openings on opposite sides alined with the slots of theblocks and the openings of the pans,- the blocks being longitudinallyslidable to place their transverse openings into or out-of alignmentwith the bus and duct openings.

27. A bus duct comprising cooperating elongated sheet metal pans whichtogether form a duct, each pan having longitudinally spaced openings,longitudinally spaced insulator blocks in each pan at such openings andformed with longitudinally extending grooves on-the sides thereof mostremote from said openings and also formed with transversely extendingslots opening to said grooves and arranged to open to and aline withsaid openings, bus bars in the grooves of both sets of blocks in bothpans, and externally accessible means for fastening the pans to eachother and thus holding the blocks and bus bars in assembly, the blocksin one pan terminating short of the opposite wall of the other pan,whereby the duct is not transversely barriered completely, but is formedto permit air to flow continuously therethrough, each bus being hollowand U- shaped so that air can flow through the bus bars, and havingspaced openings in its bight alined with slots of the blocks between thebight and a pan, and thus alined with the openings of that pan, theblocks being longitudinally slidable to place their transverse openingsinto or out of alignment with the bus and duct 'openings. WILLIAM H.FRANK.

